Authored by Aleksander P. Wozniak from the University of Warsaw and Ludwik Adamowicz from the University of Arizona in collaboration with Hylleraas members Thomas Bondo Pedersen and Simen Kvaal, the paper provides further evidence that laser-driven molecular quantum dynamics without assuming the Born-Oppenheimer approximation is possible using fully flexible explicitly correlated Gaussian basis functions.
Abstract of the paper
When time-propagating a wave packet representing a molecular system interacting with strong attosecond laser pulses, one needs to use an approach that is capable of describing intricate coupled electronic-nuclear events that require departure from the conventional adiabatic Born–Oppenheimer (BO) approximation. Hence, the propagation should be carried out simultaneously for the electrons and nuclei, treating both particle types on an equal footing without invoking the BO approximation. In such calculations, in order to achieve high accuracy, the wave packet needs to be expanded in basis functions that explicitly depend on interparticle distances, such as all-particle explicitly correlated Gaussians (ECGs).
In our previous work, we employed basis sets consisting of ECGs with optimizable complex exponential parameters to fit time-dependent wave functions obtained from grid-based propagations of two model systems: a nucleus in a Morse potential and an electron in a central-field Coulomb-like potential, subjected to intense laser pulses.
In this work, we present a proof-of-principle study of the time propagation of linear combinations of ECGs for these two models using Rothe’s method. It is shown that the approach very closely reproduces the virtually exact results of grid-based propagation for both systems. This provides further evidence that ECGs constitute a viable alternative to purely grid-based simulations of coupled nuclear-electronic dynamics driven by intense laser pulses.
Publication: 2025.06.09; https://doi.org/10.1021/acs.jpca.5c01732